Thanks. I was planning to do that in the description. My worry is the 'Item Specifics' part which doesn't leave any room for ambiguity. Since ebay uses the information entered there to narrow down searches, if I don't have 100% Wool there, my item wouldn't even be seen by anyone who's looking for a wool tweed suit. I'd love to be corrected if I'm wrong in my assumptions.
Tweed is in the item specifics list. Just use that.